In a global navigation system based on satellites, the accurate detection of a specified position with regard to the earth requires local as well as global integrity. Integrity means on one hand the capability of the global navigation system to warn users within a predetermined time if parts of the system should not be used for their determined usage; on the other hand, integrity means also the trust a user can put in the reliability of the information received from the system, particularly the accuracy of the information.
Warnings are necessary if single satellite signals for the navigation contain defects. For example, such defects occur if a navigation signal of a satellite is created at the wrong time (clock or time correction error) or at the wrong place (faulty satellite orbit). These defects have an influence on the apparent run length of the signal from a satellite to a receiver and, therefore, have an strong impact on the accuracy of navigation. Time errors can also be considered as run length errors. Defects or errors are also named as signal in space error, abbreviated SISE. The name signal in space comes from the task of a global navigation system based on satellites or a satellite navigation system which disseminates signals in space in order to allow a detection of the position of a receiver of the signals.
Known concepts of integrity are based on the assumption that it is possible to perfectly detect errors. Known non-regional integrity concepts are the Wide Area Augmentation System (WAAS) and the European Geostationary Navigation Overlay Service (EGNOS). With these concepts, it is assumed that errors can always be detected. However, this assumption is not always correct and, therefore, the accuracy of navigation can be reduced.